Tooth bleaching with low-temperature plasma lowers surface roughness and Streptococcus mutans adhesion.

AIM: To evaluate the structural-morphological changes in enamel surface roughness and Streptococcus mutans adhesion after tooth bleaching using plasma in combination with a low concentration of 15% carbamide peroxide (CP). METHODOLOGY: Sixty pairs of premolars were randomly assigned to the treatment groups (n = 30; buccal surface, groups 1A/2A) or controls (n = 30; palatal surface, Groups 1B/2B). Group 1A received a low concentration of 15% CP and low-temperature plasma. Premolars in group 1B were placed in phosphate-buffered saline and served as controls. The buccal surface of Groups 2A was subjected to 15% CP alone, whilst the palatal surface was subsequently immersed in PBS (group 2B). After bleaching, all teeth were soaked for 1 h in artificial saliva at 37 degrees C. Subsequently, teeth were placed in brain-heart infusion with S. mutans at 37 degrees C for 24 h. The assessment of the structural-morphological changes was carried out using a biofilm assay, scanning electron microscopy and atomic force microscopy. Statistical analysis of the data was performed with the SPSS (SPSS Inc., Version 18.0, Chicago, IL, USA). The Student's t-test was used to determine whether there was a significant difference in the structural-morphological effects with and without plasma. RESULTS: Significantly less S. mutans adhesion was observed in group 1A compared with the other groups (P < 0.05). Moreover, the surface roughness was significantly greater in group 2A compared with the other groups (P < 0.05). CONCLUSIONS: The application of plasma did not result in any structural-morphological and topographic changes in the enamel. The combined bleaching method using plasma and a low concentration of 15% CP was less destructive, particularly with respect to tooth surface changes.